The present invention relates to novel cyclic peptides from the cyclosporin series which have a strong inhibitory effect on human immunodeficiency virus (HIV) without having any immunosuppressive activity. Such cyclic peptides are claimed, inter alia, in EP 484 281. One of the substances which is specifically claimed in this patent specification is (gamma-hydroxy-N-methylleucine)cyclosporin. While this substance can very readily be prepared from cyclosporin A by means of microbial hydroxylation, EP 484 281 indicates that this substance has an activity against HIV which is some 5-6 times weaker than that of the most strongly active substances, namely MeIle-4-cyclosporin or MeVal-4-cyclosporin. All 3 substances have practically no immunosuppressive activity. Unexpectedly, it has been found that the anti-HIV effect of (gamma-hydroxy-MeLeu-4)cyclosporin can be substantially improved, without giving rise to any immunosuppressive activities, by introducing suitable substituents into the methylene group of the amino acid sarcosine in position 3 of said cyclosporin. Since the therapeutic doses of cyclosporin A which are used after organ transplants in order to prevent rejection of the transplanted organs are very high, and similarly high doses are to be expected for an anti-HIV therapy which uses cyclosporin derivatives, the value of the present invention is that it provides novel cyclosporin derivatives which possess high anti-HIV activity and that these cyclosporin derivatives can be prepared simultaneously, in a few steps, from cyclosporin A, which is a product which is already being prepared by the ton.